ACE2 Expression And Immunity Development In Saliva Of COVID-19 Subjects

Objectives: To provide a more comprehensive understanding of the COVID-19 infection on the oral cavity and their possible involvement in the transmission of SARS-CoV-2 by the study of the salivary expression of angiotensin-converting enzyme 2 (ACE2) and the antibodies IgG and IgA specific for SARS-CoV-2 in positive COVID-19 subjects and their inhouse close contacts. Methods: There was performed a prospective cohort study with 114 primary cases diagnosed by nasopharyngeal swabs and their inhouse close contacts (n=239). All subjects were visited at their homes, underwent an anamnesis, symptoms questionnaire and periodontal condition self-report. Unstimulated saliva samples from primary cases and their inhouse close contacts (symptomatic and asymptomatic) at 7, 14, and 45-60-days post-infection were collected and the expression of (ACE2) and antibodies (IgG and IgA) expression in COVID-19 (+) patients was determined by ELISA assays. Fisher exact and T Student tests were used to evaluating the association among variables. Results: 353 subjects were recruited, 228 were positives, and 122 were negatives for SARSCoV-2 infection. In those positive for COVID-19, 54.6% express ACE2, a 98.2% IgA and a 47.3% IgG in saliva samples. A positive association between saliva concentration of ACE2 (p=0,0176) and symptoms quantity (p=0.05) was observed. The positive contact presented a higher salivary concentration of ACE2 (p-value=0.0345). Also, ACE2 was related to selfreported periodontal disease (p=0.00486), bleeding gums (p=0.0397), and tooth mobility (p=0.0185). IgA was related with the viral load in saliva (p=0.0006) and symptomatic cases have higher expression of IgA compared to asymptomatic subjects (p=0.0185). Also,
positives overweight subjects have a lower expression of IgG (p=0.03). Conclusions: The oral cavity and saliva is involved in the transmission of COVID-19, and the present results confirm the expression of SARS-CoV-2 receptor ACE2 and the development of specific antibodies against SARS-CoV-2 in saliva samples.